Multiple sclerosisTuesday, June 23, 2009, 17:30 - 19:00Cortical grey matter is spared in paediatric MS: a magnetisation transfer and diffusion tensor MRI studyM. Absinta, M.A. Rocca, A. Ghezzi, L. Moiola, V. Martinelli, G. Comi, M. Filippi (Milan, Gallarate, IT)
Objective: Contrary to what happens in adult-onset multiple sclerosis (MS), previous preliminary quantitative magnetic resonance imaging (MRI) studies showed only subtle changes in the normal-appearing brain tissues in patients with early-onset MS. Aim of this study was to evaluate the presence and extent of tissue damage in the brain normal appearing white matter (NAWM), gray matter (GM) and cervical cord from a large population of pediatric MS patients.
Methods: From 49 pediatric patients with relapsing-remitting MS and 15 sex- and age-matched healthy controls, brain dual-echo, brain pulsed gradient spin echo (PGSE) echo planar and brain and cervical cord 2D gradient echo with and without a saturation pulse sequences were acquired. Brain lesion volume (LV) was measured and cervical cord lesions were identified. Magnetization transfer ratio (MTR), mean diffusivity (MD) and fractional anisotropy (FA) maps were produced and the corresponding histograms of the NAWM and GM were derived. MTR histogram was also derived from cervical cord.
Results: In pediatric MS patients, mean brain T2 LV was 10.5 ml (range=0.02-61.4 ml), average lesion MTR was 37.6% (SD=2.6%), average lesion MD was 1.03 mm2/sx10-3 (SD=0.08), average lesion FA was 0.26 (SD=0.02), and average number of cervical cord lesion was 1.2 (range=0-7). Compared to healthy controls, pediatric MS patients had significantly increased average NAWM MD (p=0.02) and decreased average NAWM FA (p<0.0001). No diffusivity changes were found in the brain GM. No MTR changes were detected in the cervical cord. Age of disease onset was significantly correlated with average NAWM FA (r=0.54, p<0.001) and NAWM MD (r=-0.45, p=0.002). Brain LV was significantly correlated with average NAWM FA (r=-0.49, p=0.001).
Conclusions: This study confirms the paucity of the ‘occult’ CNS damage in pediatric MS patients. In these patients cortical GM is spared by the disease process, while NAWM changes are likely to be, at least partially, secondary to Wallerian degeneration of fibers passing through macroscopic lesions.
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